We have deposited epitaxial diamond films with very low angular spread on epitaxial &bgr;-phase silicon carbide layers on silicon (001) substrates. From x-ray rocking curve measurements, half-widths of the angular spread of the crystal orientation as low as 0.6° have been determined, which is the smallest value ever reported in heteroepitaxial diamond films and appears to be smaller than those of the &bgr;-phase silicon carbide underlayers. The film surface exhibits a roughness of about 100 nm with very few discernible boundaries due to misorientation. The optimization of the bias-enhanced nucleation process and the control of selective growth are the main factors for the improvement of the crystallinity. ©1997 American Institute of Physics.